Generally, in manufacturing semiconductor devices, the semiconductor devices are formed on a semiconductor wafer by performing various types of processes such as heat treatments. The heat treatments include oxidation, diffusion, chemical vapor deposition (CVD), annealing and so on.
A heat treatment apparatus may be used to process the heat treatment of a batch of wafers at a time. The heat treatment apparatus includes a processing chamber, which is configured to accommodate a wafer holder loaded with the wafers. The wafers in the processing chamber are treated by supplying a processing gas injected into the processing chamber, and residual processing gas after the heat treatment is together exhausted from the processing chamber.
However, in the processing chamber, the processing gas can be only supplied to process the whole batch of the wafers. Accordingly, improvements in the heat treatment apparatus and methods for processing wafers continue to be sought.